表的查詢數值聚集函數-count等 · 數據庫速查

[TOC=1,5] >[success] # 聚集函數 >在應用中，經常需要匯總數據而不用把它們實際檢索處理，MySQL 提供了專門的聚集操作函數，如下圖所示： ![](https://box.kancloud.cn/55e2b05df8465919539193420abc55f7_798x343.png) >[danger] ##### 返回平均值 - AVG `SELECT AVG(prod_price) AS avg_price FROM products;` ![](https://box.kancloud.cn/551efefb4ce90e8b1ffbfe3575dd9fa8_131x46.png) **注：** 配合where 條件計算 `SELECT AVG(prod_price) AS avg_price FROM products WHERE vend_id=1003;` ![](https://box.kancloud.cn/a558505057f49c9506fd32c02415fcae_127x50.png) * * * * * >[danger] ##### 返回列的行數 - count `SELECT COUNT(*) AS num_cust FROM products;` ![](https://box.kancloud.cn/58bdb4d25cb88f53825366c24d07e497_119x40.png) * * * * * >[danger] ##### 返回最大值 - max `SELECT MAX(prod_price) AS max_price FROM products;` ![](https://box.kancloud.cn/cd1f9ebe2a17e46003bc4f4d2c1132cb_127x39.png) **注：用limit** `SELECT prod_price AS max_price FROM products ORDER BY prod_price DESC LIMIT 1;` * * * * * >[danger] ##### 返回最小值 - min `SELECT min(prod_price) AS max_price FROM products;` * * * * * >[danger] ##### 返回和 - sum `SELECT SUM(prod_price) AS max_price FROM products;;` ![](https://box.kancloud.cn/34261a2449309f6aacb0ab645dafb008_138x39.png) * * * * * >[danger] ##### 將幾個函數組合使用 ![](https://box.kancloud.cn/3af257c3dcf341801f0f0f9de85bf400_822x151.png)